Adjustable shock absorber

ABSTRACT

An adjustable hydraulic shock absorber having a shock receiving piston means telescopically mounted over an axially disposed fluid metering tube means provided with a plurality of metering orifices, and means for adjusting the effective cross sectional areas of the metering orifices.

United States Patent 1 Bindon [S4] ADJUSTABLE SHOCK ABSORBER [75]Inventor: Glyn A. Bindon, Oxford, Mich.

[73] Assignee: Ace Controls, Inc.,

Mich.

[22] Filed: May 19, 1971 [21] App]. No.: 144,894

Farmington [52] US. Cl. ..l88/285, 188/287, 188/318, 213/43 [51] Int.Cl. ..Fl6f 9/44 [58] Field of Search ..188/282, 284, 285, 188/287, 289,314, 315, 317, 299, 313, 319, 318; 213/43, 8

[56] References Cited UNITED STATES PATENTS 3,168,168 Chorkey ..188/287May8, 1973 3,341,189 9/1967 Rumsey ..188/314 X 3,344,894 10/1967Kenworthy... ..188/287 3,446,317 5/1969 Gryglas ..l88/287 3,605,9609/1971 Singer ..188/314 FOREIGN PATENTS OR APPLICATIONS 315,917 7/1929Great Britain ..188/289 Primary Examiner-George E. A. HalvosaAtt0rney-Donnelly, Mentag & Harrington [5 7] ABSTRACT An adjustablehydraulic shock absorber having a shock receiving piston meanstelescopically mounted over an axially disposed fluid metering tubemeans provided with a plurality of metering orifices, and means foradjusting the effective cross sectional areas of the metering orifices.

23 Claims, 31 Drawing Figures Patented May 8, 1973 8 Sheets-Sheet 2 147"TOR/V1975" Patented Ma s,.1973' I 3,731,770 7 I 8 Sheets-Sheet 5 IINVENTOR- 6.4 m A. a/moo/v A TTOR/VE Y5 Paten fed May 8, 1973 8Sheets-Sheet 7 5 v, W w Wwk wwmm r A 4 W1. Q w w w 2 Q' 5. m 6.

ADJUSTABLE SHOCK ABSORBER SUMMARY OF THE INVENTION This inventionrelates to the adjustable hydraulic shock absorber art, and moreparticularly, to an adjustable hydraulic shock absorber having the shockreceiving piston means telescopically mounted over an axially disposedadjustable metering tube means.

It is an important object of the present invention to provide aneconomical adjustable hydraulic shock absorber which is provided with anefficient adjustment means that provides a wide range of meteringorifice adjustment with a maximum degree of insensitivity to temperaturefluctuations.

It is another object of the present invention to provide an adjustablehydraulic shock absorber which may be quickly and easily modified forspecial shock absorbing conditions and for optional type of mountings.

It is still another object of the present invention to provide anadjustable shock absorber which is provided with a metering tube meanshaving about one-third of the diameter of the prior art metering tubesused in adjustable shock absorbers so as to provide a metering tubestructure which may be more economically manufactured because of theminimum amount of surface area which must be accurately finished. Thestructure of the shock absorber of the present invention permits theratio of tube wall thickness to tube diameter to be increased becausethe tubes are relatively stiffer. The increased stiffness decreases thelikeliness of the tubes going out of round, which means that they can bemore easily finished to closer mating tolerances. The same stiffness ina large diameter tube would result in excessive material cost andgreater bulk and weight in the final product.

It is still another object of the presentinvention to provide anadjustable hydraulic shock absorber having a more simple piston cylinderwhich is provided with a smooth and uninterrupted main bore so as toprovide greater structural integrity and eliminate sharp edged orificesand thus provide longer piston life.

It is still a further object of the present invention to provide a smalldiameter metering tube means which includes a pair of relativelyrotatable tubes for varying the metering orifice size and which providesan optimum valving means since there are no large hydraulic forcestending to separate the edges of the metering orifices. The reduceddiameter tube-on-tube metering means provides an advantage of reducedtemperature sensitivity.

It is still a further object of the present invention to provide anadjustable hydraulic shock absorber having a metering tube meansprovided with a plurality of metering orifices having sharp edges which,are relatively insensitive to oil viscosity changes as a result oftemperature changes. 1

It is still a further object of the present invention to provide anadjustable hydraulic shockr absorber provided with a small diametermetering tube means which permits the increasing of orifice slot widthsas compared to the prior art large diameter metering tube means. Theability to provide increased orifice slot widths provides an orificeconstruction wherein the viscous pressure drop is substantially reducedas compared to larger diameter shock absorbers where large diametermetering tubes are employed. This improved structure provides a shockabsorber which will operate as rapidly and efficiently when it. is firststarted at the beginning of a work day as when it is used on an assemblyline after a full days use. The small diameter metering tube structureof the present invention also permits the use of a large number ofadjustable orifices without weakening the metering tubes to provideoptimum efficiency.

It is still a further object of the present invention to provide a smalldiameter metering tube means for an adjustable hydraulic shock absorberwherein the metering tubes are fitted together with close tolerances soas to hold leakage between the two to a minimum and thus provide a shockabsorber which is capable of providing linear deceleration at extremelyslow speeds.

It is still another object of the present invention to provide anadjustable shock absorber which includes a piston cylinder having oneend enclosed by a cylinder head and having port means at the other endconnected to a fluid accumulator means, a fluid metering tube meanssupported axially in the piston cylinder and provided with a pluralityof fluid metering orifices and means for adjusting the cross sectionalsides of the orifices, a shock absorbing piston means slidably mountedin the piston cylinder and being telescopically mounted over themetering tube means, said piston cylinder and metering tube means beingfilled with fluid, and a first fluid passage means for connecting theinterior of the metering tube means to said port means during a shockabsorbing operation and a second fluid passage means connecting the portmeans to the piston cylinder means during an outward movement of thepiston means.

Other features and advantages of this invention will be apparent fromthe following detailed description, appended claims, and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a broken, longitudinalsection view, with parts broken away, of an illustrative shock absorbermade in accordance with the principles of the present invention.

FIG. 2 is a left hand view of the structure illustrated in FIG. 1, takenalong the line 22 thereof, looking in the direction of the arrows, andshowing the adjusting pin for the inner metering tube moved to a 30adjustment position.

FIG. 3 is an elevational section view of the structure illustrated inFIG. 1, taken. along the line 3-3 thereof, looking in the direction ofthe arrows, and showing the adjustable inner metering tube in the fullyopen position.

FIG. 4 is an elevational section view of the structure illustrated inFIG. 1, taken along the line 4-4 thereof, and looking in the directionof the arrows.

FIG. 5 is a broken, longitudinal section view of a second embodiment ofthe invention, and showing an accumulator return means.

FIG. 6 is a fragmentary, elevational section view of a modified pistonrod combination bearing and seal means adapted to be employed in theshock absorber embodiments illustrated in FIGS. 1 and 5.

FIG. 7 is a fragmentary side elevational view of an outer fixed meteringtube adapted "to be used in shock absorbers of the present invention,and showing another type of sharp edged metering orifice.

FIG. 8 is an elevational section view of the outer metering tubestructure illustrated in FIG. 7, taken along the line 8-8 thereof, andlooking in the direction of the arrows.

FIG. 9 is an enlarged, fragmentary, elevational section view of thestructure illustrated in FIG. 8, taken along the line 9--9 thereof, andlooking in the direction of the arrows.

FIG. 10 is an enlarged, fragmentary section view of the structureillustrated in FIG. 8, taken along the line 10-10 thereof, and lookingin the direction of the arrows.

FIG. 11 is a fragmentary, side elevational view of an adjustable innermetering tube adapted to be used with the outer metering tubeillustrated in FIG. 7.

FIG. 12 is an elevational section view of the inner metering tubestructure illustrated in FIG. 11, taken along the line 12l2 thereof, andlooking in the direction of the arrows.

FIG. 13 is an elevational section view of the inner metering tubestructure of FIG. 11 rotatably mounted inside of the outer fixedmetering tube structure of FIG. 7, and showing the inner metering tubein a fully open position.

' FIG. 14 is an enlarged, fragmentary, elevational section view of thestructure illustrated in FIG. 13, taken along the line l414 thereof, andlooking in the direction of the arrows.

FIG. 15 is a fragmentary side elevational view of another outer fixedmetering tube adapted to be used in the shock absorber of the presentinvention, and showing a further type of sharp edged metering orifice.

FIG. 16 is an elevational section view of the outer metering tubestructure illustrated in FIG. 15, taken along the line 1616 thereof, andlooking in the direction of the arrows.

FIG. 17 is a fragmentary, enlarged, elevational section view of thestructure illustrated in FIG. 16, taken along the line 17l7 thereof, andlooking in the direction of the arrows.

FIG. 18 is a fragmentary side elevational view of an adjustable innermetering tube adapted to be used with the outer fixed metering tubeillustrated in FIGS. 15 through 17.

FIGS. 19 through 25 illustrate the sequence of steps employed in formingthe sharp edged metering orifices employed in the adjustable innermetering tube of FIG. 18.

FIG. 26 is a fragmentary side elevational view of an adjustable innermetering tube adapted to be used with the outer metering tubeillustrated in FIG. 15.

FIG. 27 is an elevational section view of the inner metering tubestructure illustrated in FIG. 26, taken along the line 2727 thereof, andlooking in the direction of the arrows.

FIGS. 28 through 30 illustrate some of the sequence of steps employed informing the sharp edge metering orifices employed in the adjustableinner metering tub of FIG. 26. I

FIG. 31 is a fragmentary, side elevational view of still another inneradjustable metering tube adapted to be used with the outer metering tubeillustrated in FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,and in particular to FIG. 1, wherein is shown an illustrative embodimentof the invention, the numeral 10 generally designates a shock absorbermade in accordance with the principles of the present invention. Theshock absorber 10 includes an outer piston cylinder or tube 11 in whichis slidably mounted a shock absorber piston assembly generally indicatedby the numeral 12 and which carries on its outer end a hollow or tubularpiston rod 13. The numeral 14 generally designates a tubular meteringmeans which is fixedly mounted in the outer tube 1 1 in a centrallongitudinal position, and over which is telescopically and slidablymounted the piston assembly 12 and the tubular piston rod 13.

As shown in FIG. 1, the rear end of the outer tube 11 is mounted arounda shoulder 15 that is formed on a rear cylinder head 16 that functionsas an outer tube retainer. The outer tube 11 is fixedly secured to therear cylinder head 16 by any suitable means, as by welding. The frontend of the outer tube 11 is mounted in a bore 17 in a front mountingring 18. The outer tube 1 1 may be secured to the front mounting ring 18by any suitable means, as by welding. The shock absorber 10 may be frontmounted or rear mounted, as desired. As shown in FIG. 1, a frontmounting plate 19 is releasably secured to the mounting ring 18 by aplurality of suitable machine screws 20. The front mounting plate 19 isprovided with an axial bore 21 through which passes the tubular pistonrod 13.

As shown in FIGS. 1 and 3, an accumulator cylinder or tube 24 isconcentrically mounted around the outer tube 11 and has its rear endslidably mounted over the outer periphery 27 of the cylindrical rearcylinder head 16, and has its front end slidably mounted over the outerperiphery 31 of the front mounting ring 18. The annular space 25 betweenthe outer tube 11 and the accumulator tube 24 comprises an accumulatorchamber in which is mounted a suitable cylindrical accumulator sponge26. The sponge 26 may be formed from any suitable material as forexample, it may be made from a closed cell cellular rubber material.

As shown in FIG. 1, a suitable sealing means is provided between theperiphery 27 of the rear cylinder head 16 and the accumulator tube 24 inthe form of a suitable O-ring 28 and a back-up ring 29. A releasableretaining ring 30 is mounted around and in the rear cylinder head 16,and it abuts the rear end of the accumulator tube 24. An O-ring seal 32and a back-up ring 33 are also disposed in the periphery of the frontmounting ring 18 for sealing engagement with the inner surface of theaccumulator tube 24. A releasable retaining ring 34 is operativelymounted in the outer periphery of the mounting ring 18 and abuts thefront end of the accumulator tube 24. It will be seen that the retainerrings 30 and 34 retain the accumulator tube 24 against axial movement.

As shown in FIGS. 1 and 4, the piston chamber or cylinder 37, inside theouter tube 11, is in communication with the accumulator chamber 25through an insert port 39. The port 39 is threadably mounted in a bore38, which is formed in the wall of the outer tube 11 adjacent the frontend of the shock absorber 10, but

' any other suitable means, as by welding.

As shown in FIGS. 1 and 2, the rear cylinder head 16 carries a pluralityof outwardly extended mounting lugs 40 which are each provided with athreaded axial bore 41 that extends inwardly into the cylinder head 16.The lugs 40 thus provide a means for mounting the shock absorber at therear end thereof to a suitable mounting flange or other member. a

As shown in FIG. 1, the outer tube 11 and the accumulator tube 24 areeach provided with a bleed hole as 44 and '46, respectively, which areeach adapted to be closed by a suitable bleed screw as 45 and 47,respectively.

As shown in FIGS. 1 and 3, the tubular metering means 1d comprises apair of concentrically mounted metering tubes comprising a rotatablyadjustable inner metering tube 48 and a fixed outer metering tube 49. Asshown in FIG. 1, the rear end of the inner metering tube 48 is mountedover an axially inward extended shoulder 50 which is formed on the innerside of an inner tube retainer 52. The inner tube retainer 52 is made inthe form of a substantially cylindrical plug which is rotatably mountedin a central longitudinal bore 53 formed through the cylinder head 16and having a stepped, enlarged inner'end bore 56. The rear end of theinner metering tube 48 sits against an enlarged radial flange 51 formedon the inner end of the inner tube retainer 52, and it is securedthereto by any suitable means, as by welding. A suitable combination 0-ring and back-up ring sealing means, indicated by the numeral 54, isoperatively mounted around the inner tube retainer 52 for sealingengagement with the bore 53. The inner tube retainer 52 is releasablysecured in the rear cylinder head bore 53 by a releasable retainer ring55.

As shown in FIG. 1, the rear end of the fixed outer metering tube 49 isslidably mounted in the enlarged stepped inner end 56 of the axial bore53, and in a rotatable sliding engagement with the enlarged radialflange 51 on the retainer 52.

The outer metering tube 49 is fixed against longitudinal movement by areleasable retaining ring 57' and against rotatable movement by anaxially disposed dowel pin 58. The dowel pin 58 is positioned in anaxial hole in the cylinder head 16, as by press fit, and the outer endthereof extends into a dowel pin hole 59 formed in the rear end of thewall of the outer metering tube 49.

The bore or interior chamber in the outer metering tube 49 is indicatedby the numeral 61 and the bore or interior chamber in the inner meteringtube 48 is indicated by the numeral 62. The inner tube chamber 62communicates at its rear end with an axial bore 63 formed through theinner tube retainer or plug 52. The outer end of the axial bore 63 isclosed by a threadably mounted plug 64.

As shown in FIGS. 1 and 2, the retainer or plug 52 is adapted to berotated, so as to adjust the inner metering tube 48 between open andclosed positions, by an adjusting pin 65, which is fixedly secured inthe inner tube retainer 52 by a set screw 66. The adjusting pin 65 isadapted to be moved through a 90 are so as to rotate and adjust theinner metering tube 48 between fully closed and fully opened positions.In order to indicate the adjusted setting of the inner tube 48, theupper end of the adjusting pin 65 is provided with an indicating arrowas shown in FIG. 1. The arrow on the adjusting pin 65 would bepositioned opposite the desired angle setting, as indicated by suitableangle indicia on a graduated dial 67 which is secured to the peripheryof the rear cylinder head 16 by any suitable means, as by a plurality ofscrews 68. I

As shown in FIG. 2, the inner tube retainer or plug 52 is adapted to besecured in an adjusted position by a lock screw 72 which is threadablymounted in a radially disposed tubular body 71 that is fixedly securedby any suitable means, as by welding, to the outer face of the rearcylinder head 16. The inner end of the lock screw 72 is adapted toengage the outer periphery of the retainer 52 and hold it in an adjustedposition. The lock screw 72 is adapted to be secured in a lockingposition by means ofa lock screw retainer nut 73.

As shown in FIG. 1, the front end of the inner adjustable metering tube48 is indicated by the numeral 74 and it terminates short of the frontend 75 of the outer fixed metering tube 49. As shown in FIGS. 1 and 4, aplurality of four ports 76 is formed through the front end of the outerfixed metering tube 49 in a position forward from the front end 74 ofthe inner adjustable metering tube 48.

As shown in FIGS. l and 3, the fixed outer metering tube 49 is providedwith a plurality of longitudinally spaced apart, sharp edged meteringorifices 77 which are aligned with a similar plurality of sharp edgedmetering orifices 78 formed through the wall of the adjustable innermetering tube 48 in longitudinally spaced positions.

It will be seen that by adjusting the inner metering tube 48 relative tothe fixed outer metering tube 49, the operative metering orifice crosssection area between the interior 37 of the outer tube 11 and theinterior 61 of the inner metering tube 48 will be adjusted, as desired,and in accordance with the load to be absorbed by the shock absorber 10.It will be understood that the orifices 77 and 78 are longitudinallyspaced in their respective metering tubes so as to provide a lineardeceleration and maintain a constant retarding force. The meteringorifices 77 and 78 are spaced apart exponentially and this type ofspacing is well known in the shock absorber art.

The orifices 77 and 78 may be provided with various cross-sectionalareas, in order to provide a desired type of shock absorbing effectthroughout the operating stroke of the shock absorber.

As shown in FIG. 3, the orifices 77 and 78 are shown as having anoperative arcuate length of as indicated by the numeral 79. The orifices77 and 78 will be seen from an inspection of FIGS. 1 and 3 to be groovesin the form of slots which are milled into the peripheries of the tubes48 and 49, and they are positioned so as to be aligned with each otherwhen the adjusting pin 65 is in the 90 operative position so as toprovide a fully opened position. When the adjusting pin 65 is movedcounterclockwise, as viewed in FIG. 2, to the zero position, theorifices 78 in the inner metering tube 48 will be moved counterclockwiseof the position shown in FIG. 3 so as to be disposed 90 adjusted fromthe position of FIG. 3 and to have the closed wall of the inner tube 48cover the orifices 77 in the fixed outer tube 49 and close off flowthrough the orifices. As viewed in FIG. 3, the adjusting pin 65 has beenmoved to a position of about 85. In the position shown in FIG. 1, theadjusting pin 65 is at an open position of about In FIG. 1, the numeral82 designates a shock absorber piston which is provided with an annularsleeve bearing 83 on its head outer diameter and which is in slidingengagement with the wall of the inner tube chamber 37. The piston 82 isalso provided around its head with a suitablepiston ring 84. The piston82 is provided with a central longitudinal bore 85 which extendscompletely therethrough and in which is received the front ends of themetering tubes 48 and 49. A suitable sleeve bearing 86 is fixedlymounted on the piston 82 in the bore 85 for sliding engagement with theouter surface of the cylindrical fixed outer metering tube 49. Asuitable combination O-ring and back-up ring sealing means 87 is mountedon the outer end of the bearing 86 in sealing engagement with the pistonbore 85 and it is secured in place by a releasable retainer ring 88 thatalso functions to hold the bearing 86 in a fixed axial working positionin the piston bore 85.

As shown in FIG. 1, the outer end of the piston 82 is reduced incross-sectional size to provide a reduced diameter outer end portion 91having a plurality of radially extended and circumferentially spacedfluid bores or passageways 92. The passageways 92 communicate with theports 76 which are formed through the fixed outer metering tube 49. Thespace between the reduced diameter piston outer end portion 91 and theinner surface of the outer tube 11 forms a passageway to permit passageof fluid from the bores 92 to the port 39 mounted in the wall of theouter tube 11 and thence to the accumulator chamber 25, as explainedmore fully hereinafter.

As shown in FIG. 1, the piston 82 is provided with a plurality oflongitudinally extended bores or passages 93 which each extendrearwardly from one of the radially extended passages 92. The rear endportion of each of the passages 93 is enlarged, as indicated by thenumeral 94. A ball check valve 95 is operatively mounted in each of theenlarged bore portions 94, and it is adapted to be moved by fluidpressure between a valve seat formed on the end of the bore 93 where itmeets the enlarged bore portion 94 and a transverse retaining pin 96.Each of the retaining pins 96 is fixedly mounted in the piston at apoint spaced apart rearwardly from each of the ball check valve seats soas to permit the respective ball check valve 95 to be moved off of theball check valve seat under certain fluid flow conditions, and yet beretained in the respective enlarged bore portion 94, as explained morefully hereinafter. As shown in FIG. 3, there are four of theaforementioned enlarged bore portions 94 in which are seated the ballcheck valves 95.

As shown in FIG. 1, the inner end of the tubular piston rod 13 isthreadably mounted in a threaded bore 101 in the piston 82. The pistonrod 13 is secured in place in the bore 101 by any suitable means, as bya set screw 100. As shown in FIG. 3, the outer shock absorbing end ofthe piston rod 13 is enclosed by a suitable end plug 102 which is fixedin place by any suitable means, as by welding. The end plug 102 isprovided with the reduced inner end 103 around which is positioned theouter end of a suitable return spring 104. The inner end of the returnspring 104 is operatively seated on a spring retainer collar 105 whichis operatively mounted on the front end of the fixed outer metering tube49.

The rod end plug 102 is provided with a bleed hole 106 and a bleed screw107 for bleeding the interior of the tubular piston rod 13. Bleed hole106 communicates with a stepped, enlarged bore 109 in which isthreadably mounted a plug 108. In lieu of the plug 108, a suitable steelcap or button may be secured to the piston rod 13 by a bolt threadedinto the bore 109.

As shown in FIG. 1, a suitable cylindrical gland retainer 111 is fixedlymounted in the outer end of the outer tube 11 and it limits the outwardmovement of the piston 82 and the rod 13. A suitable O-ring 112 with aback-up ring 113 is operatively mounted in the outer periphery of thegland retainer 1 11 for sealing engagement with the outer tube 11. Thegland retainer 111 is retained in an axial position in the outer tube 11by means of a pair of retainer rings 114 and 116 which are spaced apartby a retainer tube 115. It will be seen that the retainer ring 114 ismounted in a suitable groove in the outer tube 1 1 and the retainer ring116 is mounted in a suitable groove in the gland retainer 1 1 1.

A piston rod sleeve bearing 117 is supported on the gland retainer 111by a pair of retainer rings 118 and 119. The retainer rings 118 and 119are mounted in suitable grooves in the inner periphery of the glandretainer 111 and they hold the bearing 117 against axial movement. Asuitable seal 120 in the form of a U- shaped cup seal, is operativelymounted on the outer side of the retainer ring 119 and it is held inaxial position by a seal retainer ring 123 and a first retainer ring122. A wiper ring 121 is mounted on the outer side of said firstmentioned retainer ring 122 and it is held in position by a secondretainer ring 122. The retainer rings 122 are mounted in suitablegrooves in the inner periphery of the retainer gland 1 11.

The operation of the adjustable hydraulic shock absorber of the presentinvention will be obvious from the aforegoing description. However, thefollowing resume will also be given. The shock absorber 10 would bemounted in an operative supporting structure with the piston rod 13 inthe extended position shown in FIG. 1 for the reception of a load. Theaccumulator chamber 25, the chamber 37 in the outer tube 11, the chamber62 in the inner metering tube 48, and the interior of the tubular pistonrod 13, would be filled with a suitable pressurized hydraulic fluid. Thefluid would be selectively admitted through one of the bleed holes 44,46 or 106. The bleed screws 47 and 107 are used to bleed off any air inthe system. The adjusting pin 65 is then turned to the proper settingfor the load which is to be absorbed. On the application of a load, or aweight impacting on the outer end of the tubular piston rod 13, the rod13 and the piston 82 start moving inwardly, or to the left as viewed inFIG. 1, and the piston 82 forces the hydraulic fluid or oil from thechamber 37 in the outer tube 11 through the metering orifices 77 and onthrough the metering orifices 78 into the passage or chamber 62 in theinner metering tube 48. The fluid is then forced to the right, as viewedin FIG. 1, and out through the ports 76 and thence through the passages92 and out through the port 39 into the accumulator chamber 25. Thehydraulic fluid entering the accumulator chamber 25 is under pressureand compresses the closed cellular rubber accumulator sponge 26. Theresistance to fluid flow through the metering orifices 77 and 78 governsthe shock absorbers internal pressure which in turn sets up resistingforces to stop the load or weight impacting on the piston rod 13. Acontrolled deceleration, and soft and smooth stopping of the load isaccomplished because the kinetic energy of the moving piston rod 13 andpiston 82 is absorbed throughout the length of stroke of the piston 82,and it approaches zero at the end of the stroke due to the longitudinalspacing of the metering orifices.

It will be seen that the metering orifices 78 in the adjustable tube 48are formed with a larger width than the orifices 77 and that they areextended throughout an arc of 90. As shown in FIG. 3, when the innertube 48 is rotated to the 90 open position the arcuate orifices 77 and78 are aligned so as to permit full flow of hydraulic fluidtherethrough. As the adjusting pin 65 is moved from the zero position,the effective cross sec tional area of each of the metering orifices orslots 77 is reduced to provide a controlled velocity at which the fluidwill be discharged from the outer tube chamber 37 into the innermetering tube 48 to control the deceleration of the load.

It will be seen that on the movement of the piston 82 inwardly, theaccumulator sponge 26 is compressed by the incompressible hydraulicfluid, and that on the return stroke upon removal of the load the returnspring 104 returns the piston 82 and the piston rod 13 to the initialposition. During the return stroke the ball check valves 95 are moved tothe left, as viewed in FIG. 1, against the retainer pins 96 so as toallow the hydraulic fluid to pass from the accumulator chamber 25 andthrough the port 39, the passages 92 and 93, and out through thepassages 94 into the chamber 37 in the outer tube 11 to again put theshock absorber in a shock absorbing condition. The cellular accumulatorsponge 26 expands back to its original shape. it will be understood thatthe shock absorber 10 is adapted to be precalibrated for known loads orweights so that the ad justing pin 65 may be set relative to the indiciaon the graduated dial 67 for various loads.

It will also be understood that the widths of the orifices 77 and 78would be made in accordance with the desired velocities for controllingthe deceleration of loads in accordance with the capacity to which theshock absorber is to be designed.

The adjustable shock absorber of the present invention provides a lessexpensive and more efficient adjustment means when compared with theprior art adjustable shock absorbers. It also yields a wider range ofadjustment with a greater degree of insensitivity to temperatu'refluctuations than the prior art adjustable shock'absorbers. It is alsoadapted to be easily modified to special conditions and optionalmountings. The diameter of the metering tubes of the shock absorber ofthe present invention is about one-third of the diameter of the meteringtubes used in the prior art adjustable shock absorbers, and thisstructure results in manufacturing economy because the smaller diametermetering tubes have only one-third of the surface area which must beaccurately finished as compared to the prior art structures. Thestructure of the shock absorber of the present invention permits theratio of tube wall thickness to tube diameter to be increased becausethe tubes are relatively stiffer. The increased stiffness decreases thelikeliness of the tubes going out of round, which means that they can bemore easily finished to closer mating tolerances. The same stiffness ina large diameter tube would result in excessive material cost andgreater bulk and weight in the final product.

It will also be seen that because the metering tubes 48 and 49 areseparate from the main bore of the outer tube or piston cylinder 11 thatthe main bore of the piston cylinder 11 is simplified by not having aseries of orifices machined in it. This main bore is smooth anduninterrupted and provides greater structural integrity as compared tothe prior art shock absorbers. The piston 82 may have greater designflexibility. The bearings and seals on the piston 82 may benon-metallic, which is an advantage when the shock absorber must be usedwith hydraulic fluids having low lubricating qualities. The resultingsimplified bearings and seals provide economy since they are alsosubject to less wear because they do not have to cross sharp edgedorifices or holes on the main bore of the tube 11, and accordingly, theywill last longer and need not be replaced as often.

The small diameter metering tubes 48 and 49, which are relativelyrotatable upon each other to vary the metering orifice size, provide anoptimum valving means since there are no large hydraulic forces tendingto separate the edges of the metering orifices. The reduced diametertube-on-tube metering means of the present invention also provides theadvantage of reduced temperature sensitivity. In a hydraulic shockabsorber, the pressure drop to absorb the energy is generated at themetering orifices. It is well known that a knife edge or a sharp edgeorifice is relatively insensitive to oil viscosity changes as a resultof temperature changes. It is relatively difficult to produce a sharpedged orifice in a narrow slot around a circumference of a largemetering tube. However, with the reduced tube circumference of themetering tubes 48 and 49 as employed in the present invention, it ispossible to provide the same orifice area by increasing the slot width.The ability to provide increased slot widths provides an orificeconstruction wherein the viscous pressure drop is substantially reducedas compared to larger diameter shock absorbers where large diametermetering tubes are employed. This means that the shock absorber of thepresent invention will operate as rapidly and efficiently when it isfirst started at the beginning of a work day when it is used on anassembly line as compared to when it has been running after a. full daysuse. The shock absorber of the present invention also may be used on anautomated assembly line or the like to provide a constant time cycle,whereby its use will not upset the synchronization of such a line,regardless of the time of the day or period over which it has been used.It is well known that the largest practical number of orifices providesthe greatest efficiency in a linear deceleration shock absorber. Theshock absorber of the present invention permits the use of a largenumber of adjustable orifices without weakening the metering tubes, toprovide optimum efficiency, and this is possible because the orificecircumference is reduced with the small diameter metering tubes 48 and49, as compared to the prior art large metering tubes.

The small diameter metering tubes 48 and 49 with their close fittingtolerances hold leakage between the tubes to a minimum, and accordingly,the structure is adapted to provide a shock absorber which is capable ofproviding linear deceleration at extremely low speeds.

FIG. illustrates a modified embodiment of the invention wherein thereturn spring is eliminated, and an outside pneumatic return forceacting through an airoil tank is used. The parts of the embodiment ofFIG. 5 which correspond to the parts of the embodiment of FIGS. 1through 4 have been marked with the same reference numerals followed bythe small letter a.

In the embodiment of FIG. 5, the accumulator cylinder 24 and sponge 26have been eliminated. The port 390 is directly connected to a suitablefluid conduit 125 which is operatively connected to a suitable air-oilaccumulator tank 126. The accumulator tank 126 may be any conventionalair-oil tank which is half filled with oil in the lower end thereof andwhich is provided with air under pressure in the top end thereof. Thenumeral 124 designates an air line which is connected at one end to theaccumulator tank 126 and which would be connected at the other end to asuitable source of pressurized air. It will be understood that the shockabsorber illustrated in FIG. 5 functions in the same manner as the shockabsorber illustrated in FIGS. 1 through 4, but that the return forcewould be provided by the air-oil pneumatic system illustrated.

FIG. 6 is a fragmentary illustration of a modified piston structure. Theparts of the piston structure illustrated in FIG. 6 which are the sameas the first embodiment of FIGS. 1 through 4 have been marked with thesame reference numerals followed by the small letter b. The onlydifference between the piston structure of FIG. 6 and that of FIG. 1 isthat the sleeve bearing 83 and the piston ring 84 have been replaced bya single sleeve bearing 83b which may be made from any suitablematerial, including a non-metallic material. It will be seen that ashock absorber provided with a single dynamic seal as 83b and the twostatic seals 117 and 120 may be pressurized to very high returnpressures, such as pressures obtained in hydraulic pumps or highpressure nitrogen accumulators. The shock absorber of the presentinvention is thus adapted to withstand larger than normal repositioningforces. The piston area of the return piston 82 is relatively large, andit is light in weight and rigid in construction, as compared to thepiston rods used in prior art shock absorbers.

FIGS. 7 through 10 illustrate another outer fixed metering tube whichmay be used in a shock absorber of the present invention. The parts ofthe metering tube illustrated in FIGS. 7 through 10 which are the sameas the metering tube 49 in the embodiment of FIGS. 1 through 4 have beenmarked with the same reference numerals followed by the small letter 0.

As shown in FIGS. 7 and 9, the metering orifices 77c comprise taperedslots which extend through a 90 angle arc, as indicated by the numeral132 in FIG. 8. The tapered slots 77c are formed by cutting a taperedgroove in the outer surface of the tube 490 with a suitable cutting toolwhich is so positioned that it cuts through the inner surface of thetube 490 between two arcuate points which are 90 apart as indicated bythe numeral 132. The numeral 127 in FIG. 8 designates the diameter ofthe tube 490. The numeral 128 indicates tapered slots which provides anextremely sharp edged metering orifice. The numeral 134 designates thewidth of the inner sharp edge 133 of the metering orifice, which wouldextend throughout the 90 arc. The width 134 would depend in each case onthe desired deceleration characteristics and the size of the shockabsorber. The fixed outer metering tube 490 functions in the same manneras the previously described metering tube 49, and it is adapted tofunction in the same manner with the previously described adjustableinner metering tube 48. It will be seen that the cross sectional area ofthe orifices 770 are truncated in cross section while the cross sectionof the orifices 77 are substantially rectangular.

FIGS. 11 and 12 illustrate a second embodiment of an adjustable innermetering tube which may be employed in the shock absorber of the presentinvention. The parts of the inner metering tube illustrated in FIGS. 11and 12 which are the same as the metering tube 48 of the embodiment ofFIGS. 1 through 4 have been marked with the same reference numeralsfollowed by the small letter c. In the embodiment of FIGS. 11 and 12,the metering slot orifice 780 is formed in a stepped fashion with anouter slot portion 137 being formed to a first width, and the inner slotportion 138 being formed to a second and narrower width. The narrowwidth orifice portion 138 would be preferably formed by a flat millingcutter which would be passed through the periphery of the tube 480, andthrough the inner periphery thereof, so as to form a slot having anarcuate length of 90, as indicated by the numeral 142. The enlargedwidth outer orifice portion 137 would preferably be formed with a rotarymilling cutter which would cut through the wall of the tube 48c in thepath of the narrow slot 138 but on an arcuate path formed by the radius139 which is shown as extending from a center point or radius point 140.It will be seen that the orifice 780 is provided with a sharp edge alongthe arcuate junction point between the enlarged orifice portion 137 andthe narrow orifice portion 138. The relative widths of the orificeportions 137 and 138 are indicated by the numerals 143 and 141respectively, in

FIG. 11.

The inner adjustable metering tube 480 would function in the same manneras the inner metering tube 48. FIGS. 13 and 14 illustrate the rotatablemounting of the inner tube 48c in the aforedescribed outer metering tube490. However, it will be understood that the inner metering tube 480could also be used with the outer metering tube 49 of FIG. 1.

FIGS. 15, 16 and 17 illustrate still another modified outer fixedmetering tube, and the parts thereof which are the same as the outermetering tube 49 of FIG. 1 have been marked with the same referencenumerals followed by the small letter d. In the embodiment of FIGS. 15,16 and 17, the metering orifice 77d comprises an outer, enlarged widthslot portion 144 and an inner narrower width slot portion 145. Theorifice portions 144 and 142 may be formed by any suitable means, as bya milling cutter which would pass through the inner wall of the tube 49dwhen making the narrow orifice portion 145 so as to provide an arcuateslot orifice opening extending through 90. A second wider, or thicker,milling cutter as 146 would then be used to form the outer wider slotportion 144 which has its ends extended beyond the 90 narrow innerportion 145, as shown in FIG. 16.

FIG. 17 indicates the relative widths of the orifice portions 144 and145 and they would be made in accordance with the flow capacity desired.However, it will be seen that the orifice structure of FIGS. 15 through17 provides an extremely sharp edged orifice at the junction pointbetween the enlarged portion 144 and the narrow portion 145. The outerfixed metering tube 49d functions in the same manner as the outermetering tube 49 of FIG. 1, and it is also adapted to function with theinner metering tube 480.

FIG. 18 illustrates a modified inner metering tube provided with sharpedged orifices and with pressure relief grooves on each side of eachorifice which limit the size of the force tending to separate the innertube from an outer tube in the zone adjacent to the orifices.

FIGS. 19 through 25 illustrate the steps of one suitable method forforming the orifices of this embodiment together with the pressurerelief grooves. The parts of the inner metering tube illustrated inFIGS. 18 through 25 which are the same as the inner metering tube 48 ofthe embodiment of FIG. 1 have been marked with the same referencenumerals followed by the small letter d.

In FIG. 18, the numeral 148 designates the final sharp edge orificeslots which are formed through the wall of the tube 48d. The numerals150 in FIG. 18 designate the tapered pressure relief grooves 150 whichare formed on each side of each of the orifices 148. The final sharpedged orifices 148 may be formed in the following described manner.

As shown in FIG. 19, a first slot 151 is cut through the wall of thetube 48d to the desired width and throughout the desired 90 arc. Asshown in FIGS. and 21 a cutting tool 152 is then used to form reliefgrooves 150, in the outer surface of the tube 48d to a first depth. Thetool 152 has a rounded nose 153 and a pair of spaced side cutting edges154 for cutting the grooves 150. A cold forming or swadging tool 155, asshown in FIG. 22, is next rolled throughout the length of the slot 151.As shown in FIGS. 22 and 24, the

157 and 158, as shown in FIG. 22, which are slightly beyond the arcuateends of the original slot 151. The tube 48d is then subjected to a finehoning or grinding operation on its outer periphery so that its outersurface is ground down to the condition shown in FIG. 25, whereby therounded slot edges 159 are ground off to provide a sharp orifice edge160 for the outer orifice slot 148. The sharp edged slot 148 thusbecomes the metering orifice and its inner portion 151 is an enlargedcontinuation of the slot. The inner metering tube 48d functions in thesame manner as the previously described inner metering tubes and it isadapted to function with any of the aforedescribed outer metering tubes.

FIGS. 26 through 30 illustrate another modified adjustable innermetering tube adapted to be used with the outer metering tubes of theshock absorber of the present invention. The parts of the embodiment ofFIGS. 26 through 30 which are the same as the embodiment of FIG. 1 havebeen marked with the same reference numerals followed by the smallletter e. The sharp edged metering orifices. of this embodiment areindicated by the numeral 167 in FIGS. 26 and 27. FIGS. 28, 29 and 30indicate the steps that may be followed in forming the sharp edgedorifices 167 which extend throughout a arc. As shown in FIGS. 28 and 29,a first orifice 163 is cut as a slot through the periphery of the wallof the tube 48e. The orifice slot 163 is cut through the arc of 90 andto the desired width. A pair of grooves are then cut around the entireperiphery of the tube 48e on opposite sides of each of the orifice slots163 and to a desired depth and width. As shown in FIG. 29 the grooves164 are cut to a width of about three times the width of the orificeslots 163. A cold forming round edged tool is then rolled against theouter periphery of the grooves 164 and the slots 163 so as to cold formthe tube peripheral area making a sharp edged narrow orifice slot 167that extends throughout the 90 arc, and at the same time flatten off thematerial extended between the grooves 164 and form a concave pressurerelief groove 166 that extends around the periphery of the tube 48e.

The cold rolling and forming operation leaves a pair of radially outwardextended circumferential projections or lips 169 which are removed by asuitable honing or grinding operation so as to provide the finishedsmooth surfaced configuration illustrated in FIGS. 26 and 27. Anenlarged bleed hole 165 is formed in the Y outer surface of the tube 48eat a position diametrically swadging or cold forming tool 155 isprovided with a peripherally extended and rounded forming edge 156 whichextends throughout one-half of the circumference of the tool. The tooledge 156, as shown in FIG. 24, is extended into the slot 151. The tool155 is provided with a pair of tapered shoulders which extend into thegrooves 151. It will be seen from FIG. 24 that the peripheral formingedge 156 is narrower in width than the original orifice slot 151,whereby when the swadging tool 155 is rolled and forced inwardly againstthe tube 48d the tool will extend the pressure relief grooves inward andat the same time force the outer edges of the slot 151 over to provide anarrow outer slot 143 having rounded edges 159. The rolling and coldforming tool is rolled between the points opposite to each of theorifice slots 167 and it communicates with the interior of the tube 48ethrough a hole 168. The leakage fluid under pressure which passes aroundand through the grooves 166 and into the holes and through the holes 168provides a balancing effect on the inner tube 48e relative to itsposition inside of a mating fixed outer metering tube. The innermetering tube 48e functions in the same manner as the otheraforedescribed inner metering tubes, and it also functions with any ofthe aforedescribed outer fixed metering tubes.

FIG. 31 illustrates still another modified adjustable inner meteringtube in which the parts corresponding is constructed the same as theinner metering tube of FIGS. 26 through 30, with the exception that thepressure relief grooves 166f are only extended throughout the length ofthe orifice slots 167f, and the holes 165 and 168 are eliminated. Theinner metering tube 48f functions in the same manner as theaforedescribed inner metering tube 48.

While it will be apparent that the preferred embodiments of theinvention herein disclosed are well calculated to fulfill the objectsabove stated, it will be appreciated that the invention is susceptibleto modification, variation and change.

What is claimed is:

1. In an adjustable hydraulic shock absorber, the combinationcomprising:

a. a piston cylinder filled with fluid and having one end enclosed by acylinder head and having port means at the other end thereof;

b. a fluid accumulator means connected to said port means for receivingfluid under pressure from said port means during a shock absorbingoperation and for returning fluid to the port means after a shockabsorbing operation;

c. a fluid metering tube means filled with fluid and supported axiallyin said piston cylinder and provided with a plurality of fluid meteringorifices communicating the interior of said metering tube means withsaid piston cylinder and providing a controlled flow of fluid from saidmetering tube means during a shock absorbing operation;

d. a piston means slidably mounted in said piston cylinder and beingtelescopically mounted over said metering tube means for receiving ashock and for absorbing said shock during an inward movement from aninitial position into the piston cylinder, and which is adapted to bemoved outward to said initial position after the shock absorbing inwardmovement;

e. adjustment means operatively connected to said metering tube meansfor adjusting the effective cross sectional area of said meteringorifices to adjust the flow of metered fluid through said metering tubemeans to provide a controlled shock absorbing inward movement of saidpiston means;

f. a first fluid passage means connecting the interior of said meteringtube means to said port means for passage therethrough of fluid forcedfrom the piston chamber and into said metering tube means during aninward shock absorbing movement of said piston means, and, a secondfluid passage means connecting said port means to said piston cylinderduring an outward movement of said piston means to said initial positionfor transferring fluid from said accumulator means to said pistoncylinder;

g. said fluid metering tube means comprising a fixed metering tubehaving a plurality of metering orifices, and an adjustable metering tubehaving a plurality of metering orifices adapted to be aligned with saidmetering orifices in said fixed metering tube and being connected tosaid adjustment means;

b. said piston means including a tubular piston rod for telescopicallyreceiving the inner end of said fluid metering tube means;

i. said fixed metering tube having the outer end supported by saidcylinder head;

j. said adjustable metering tube being rotatably mounted within saidfixed metering tube and being rotatably supported by said cylinder headand being connected to said adjustment means;

k. said first fluid passage means including a plurality of ports formedthrough the inner end of said fixed metering tube which communicate withthe interior of the metering tube means, and a first plurality ofcommunicating passages through said piston means for connecting theinterior of said metering tube means with said first named port meansduring an inward movement of said piston means; and

1. said second fluid passage means including a second plurality ofpassages formed through said piston means and connected to said firstplurality of passages through said piston means and communicating thepiston cylinder with said port means, and each of said second pluralityof passages through said piston means having a ball check valveoperatively mounted therein for closing said second plurality ofpassages during a shock absorbing inward movement of said piston meansand for opening said second plurality of passages during an outwardmovement of said piston means.

2. An adjustable shock absorber as defined in claim 1, wherein:

a. each of the metering orifice slots in said adjustable metering tubeincludes a first width outer portion and a second narrower width innerportion.

3. An adjustable shock absorber as defined in claim 1, wherein:

a. said fluid accumulator means is a separately formed accumulatormeans. 4. An adjustable shock absorber as defined in claim 1, including:

a. a return spring means mounted in said tubular piston rod. 5. Anadjustable shock absorber as defined in claim 1, including:

1, including:

a. means for mounting the shock absorber in an operative position. 7. Anadjustable shock absorber as defined in claim 1, wherein:

a. said piston means is provided with an internal sleeve bearing and apiston ring for slidably mounting the piston means on said metering tubemeans.

8. An adjustable shock absorber as defined in claim 1, wherein:

a. said piston means is provided with an internal nonmetallic sleevebearing for slidably mounting the piston means on said metering tubemeans.

9. An adjustable shock absorber as defined in claim 1, wherein:

a. said plurality of fluid metering orifices in said fixed andadjustable metering tube are longitudinally spaced apart in anexponential manner to provide a controlled linear deceleration.

10, wherein:

10. An adjustable shock absorber as defined in claim 1 wherein:

a. the metering orifices in said fixed metering tube each comprises aperipheral slot cut through the wall thereof and extending throughout apredeter- 5 mined arcuate length; and,

b. the metering orifices in said adjustable metering tube each comprisesa peripheral slot cut through the wall thereof and extending throughoutsaid predetermined arcuate length and being of a width larger than theperipheral slots cut through the fixed metering tube.

11. An adjustable shock absorber as defined in claim 10, wherein:

a. each of the metering orifice slots in said fixed metering tubeincludes a first width outer portion and a second narrower width innerportion.

12. An adjustable shock absorber as defined in claim a. each of saidmetering orifice slots in said fixed metering tube comprises an inwardlytapered peripheral slot.

13. An adjustable shock absorber as defined in claim 12, wherein:

a. each of the metering orifice slots in said adjustable metering tubeis provided with a central reduced width portion for alignment with thereduced inner end of a metering orifice tapered slot in the fixedmetering tube.

3 14. An adjustable shock absorber as defined in claim 0 10, wherein:

a. each of the metering orifice slots in said adjustable metering tubeis provided with a fluid pressure relief groove on each side thereof.

15. An adjustable shock absorber as defined in claim 14, wherein:

114, wherein:

a. said pressure relief grooves extend completely around the adjustablemetering tube.

17. An adjustable shock absorber as defined in claim 16, wherein:

a. said adjustable metering tube is provided with pressure reliefopenings communicating with said pressure relief grooves.

18. An adjustable shock absorber as defined in claim 14, wherein:

a. each of said metering orifice slots in said adjustable metering tubeis formed by first cutting a peripheral slot through the wall of theadjustable metering tube, cutting a rectangular cross section groovealong each side of said last named slot, rolling over the edges,longitudinally of the tube of said last named slot and grooves to form aconcave groove with a sharp edged metering slot disposed in the deepestpart of the concave groove, and grinding the outer surface of the ad usable metering tube. 19. An adjustable shock absorber as defined in claim18, wherein:

a. the rectangular cross section groove along each side of said slot isextended around the entire circumference of the adjustable metering tubeso as to provide a concave groove extending completely around theadjustable metering tube.

20. An adjustable shock absorber as defined in claim 1 wherein:

a. said fluid accumulator means comprises a cylinder concentricallymounted around said piston cylinder and provided with an accumulatorsponge means.

21. An adjustable shock absorber as defined in claim 20, wherein:

a. the fluid in said piston cylinder, fluid metering tube means andfluid accumulator means is under pressure.

22. An adjustable shock absorber as defined in claim 1, wherein:

a. said adjustment means includes a retainer which is attached to saidadjustable metering tube and which is rotatably mounted in said cylinderhead.

23. An adjustable shock absorber as defined in claim 22, wherein:

a. said adjustment means includes an adjusting pin secured to saidretainer for rotatably adjusting said retainer and adjustable meteringtube in accordance with an arcuate adjustment scale on the outerperiphery of said cylinder head which is marked'with adjustment indicia.

1. In an adjustable hydraulic shock absorber, the combinationcomprising: a. a piston cylinder filled with fluid and having one endenclosed by a cylinder head and having port means at the other endthereof; b. a fluid accumulator means connected to said port means forreceiving fluid under pressure from said port means during a shockabsorbing operation and for returning fluid to the port means after ashock absorbing operation; c. a fluid metering tube means filled withfluid and supported axially in said piston cylinder and provided with aplurality of fluid metering orifices communicating the interior of saidmetering tube means with said piston cylinder and providing a controlledflow of fluid from said metering tube means during a shock absorbingoperation; d. a piston means slidably mounted in said piston cylinderand being telescopically mounted over said metering tube means forreceiving a shock and for absorbing said shock during an inward movementfrom an initial position into the piston cylinder, and which is adaptedto be moved outward to said initial position after the shock absorbinginward movement; e. adjustment means operatively connected to saidmetering tube means for adjusting the effective cross sectional area ofsaid metering orifices to adjust the flow of metered fluid through saidmetering tube means to provide a controlled shock absorbing inwardmovement of said piston means; f. a first fluid passage means connectingthe interior of said metering tube means to said port means for passagetherethrough of fluid forced from the piston chamber and into saidmetering tube means during an inward shock absorbing movement of saidpiston means, and, a second fluid passage means connecting said portmeans to said piston cylinder during an outward movement of said pistonmeans to said initial position for transferring fluid from saidaccumulator means to said piston cylinder; g. said fluid metering tubemeans comprising a fixed metering tube having a plurality of meteringorifices, and an adjustable metering tube having a plurality of meteringorifices adapted to be aligned with said metering orifices in said fixedmetering tube and being connected to said adjustment means; h. saidpiston means including a tubular piston rod for telescopically receivingthe inner end of said fluid metering tube means; i. said fixed meteringtube having the outer end supported by said cylinder head; j. saidadjustable metering tube being rotatably mounted within said fixedmetering tube and being rotatably supported by said cylinder head andbeing connected to said adjustment means; k. said first fluid passagemeans including a plurality of ports formed through the inner end ofsaid fixed metering tube which communicate with the interior of themetering tube means, and a first plurality of communicating passagesthrough said piston means for connecting the interior of said meterinGtube means with said first named port means during an inward movement ofsaid piston means; and l. said second fluid passage means including asecond plurality of passages formed through said piston means andconnected to said first plurality of passages through said piston meansand communicating the piston cylinder with said port means, and each ofsaid second plurality of passages through said piston means having aball check valve operatively mounted therein for closing said secondplurality of passages during a shock absorbing inward movement of saidpiston means and for opening said second plurality of passages during anoutward movement of said piston means.
 2. An adjustable shock absorberas defined in claim 1, wherein: a. each of the metering orifice slots insaid adjustable metering tube includes a first width outer portion and asecond narrower width inner portion.
 3. An adjustable shock absorber asdefined in claim 1, wherein: a. said fluid accumulator means is aseparately formed accumulator means.
 4. An adjustable shock absorber asdefined in claim 1, including: a. a return spring means mounted in saidtubular piston rod.
 5. An adjustable shock absorber as defined in claim1, including: a. a return spring means operatively mounted in said shockabsorber for returning the piston means to the initial position after ashock absorbing inward movement.
 6. An adjustable shock absorber asdefined in claim 1, including: a. means for mounting the shock absorberin an operative position.
 7. An adjustable shock absorber as defined inclaim 1, wherein: a. said piston means is provided with an internalsleeve bearing and a piston ring for slidably mounting the piston meanson said metering tube means.
 8. An adjustable shock absorber as definedin claim 1, wherein: a. said piston means is provided with an internalnon-metallic sleeve bearing for slidably mounting the piston means onsaid metering tube means.
 9. An adjustable shock absorber as defined inclaim 1, wherein: a. said plurality of fluid metering orifices in saidfixed and adjustable metering tube are longitudinally spaced apart in anexponential manner to provide a controlled linear deceleration.
 10. Anadjustable shock absorber as defined in claim 1, wherein: a. themetering orifices in said fixed metering tube each comprises aperipheral slot cut through the wall thereof and extending throughout apredetermined arcuate length; and, b. the metering orifices in saidadjustable metering tube each comprises a peripheral slot cut throughthe wall thereof and extending throughout said predetermined arcuatelength and being of a width larger than the peripheral slots cut throughthe fixed metering tube.
 11. An adjustable shock absorber as defined inclaim 10, wherein: a. each of the metering orifice slots in said fixedmetering tube includes a first width outer portion and a second narrowerwidth inner portion.
 12. An adjustable shock absorber as defined inclaim 10, wherein: a. each of said metering orifice slots in said fixedmetering tube comprises an inwardly tapered peripheral slot.
 13. Anadjustable shock absorber as defined in claim 12, wherein: a. each ofthe metering orifice slots in said adjustable metering tube is providedwith a central reduced width portion for alignment with the reducedinner end of a metering orifice tapered slot in the fixed metering tube.14. An adjustable shock absorber as defined in claim 10, wherein: a.each of the metering orifice slots in said adjustable metering tube isprovided with a fluid pressure relief groove on each side thereof. 15.An adjustable shock absorber as defined in claim 14, wherein: a. each ofsaid metering orifice slots in said adjustable metering tube is formedby first cutting a peripheral slot through the wall of the adjustablemetering tube, cutting a tapered groove along each side of said lastnamed slot, rolling over thE edges longitudinally of the tube of saidlast named slot, and grinding the outer surface of the adjustablemetering tube to form a sharp edged metering orifice slot.
 16. Anadjustable shock absorber as defined in claim 14, wherein: a. saidpressure relief grooves extend completely around the adjustable meteringtube.
 17. An adjustable shock absorber as defined in claim 16, wherein:a. said adjustable metering tube is provided with pressure reliefopenings communicating with said pressure relief grooves.
 18. Anadjustable shock absorber as defined in claim 14, wherein: a. each ofsaid metering orifice slots in said adjustable metering tube is formedby first cutting a peripheral slot through the wall of the adjustablemetering tube, cutting a rectangular cross section groove along eachside of said last named slot, rolling over the edges, longitudinally ofthe tube of said last named slot and grooves to form a concave groovewith a sharp edged metering slot disposed in the deepest part of theconcave groove, and grinding the outer surface of the adjustablemetering tube.
 19. An adjustable shock absorber as defined in claim 18,wherein: a. the rectangular cross section groove along each side of saidslot is extended around the entire circumference of the adjustablemetering tube so as to provide a concave groove extending completelyaround the adjustable metering tube.
 20. An adjustable shock absorber asdefined in claim 1, wherein: a. said fluid accumulator means comprises acylinder concentrically mounted around said piston cylinder and providedwith an accumulator sponge means.
 21. An adjustable shock absorber asdefined in claim 20, wherein: a. the fluid in said piston cylinder,fluid metering tube means and fluid accumulator means is under pressure.22. An adjustable shock absorber as defined in claim 1, wherein: a. saidadjustment means includes a retainer which is attached to saidadjustable metering tube and which is rotatably mounted in said cylinderhead.
 23. An adjustable shock absorber as defined in claim 22, wherein:a. said adjustment means includes an adjusting pin secured to saidretainer for rotatably adjusting said retainer and adjustable meteringtube in accordance with an arcuate adjustment scale on the outerperiphery of said cylinder head which is marked with adjustment indicia.